Hydrojet propulsion systems



March 23, 1965 F. J. KENEFICK 3,174,454

HYDROJET PROPULSION SYSTEMS Filed Dec. 7. 1961 E E"... J.

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L FRANCIS J. KENEFICK 44 BY 2 g (A Z74/ I" A 46 ATTORNEYS United States Patent C) 3,174,454 'HYDROJET PROPULSION SYSTEMS Francis J. Keuefick, 2354 Marcia Drive, Pleasant Hill, Calif. Filed Dec. 7, 1961, Ser. No. 157,788 4 Claims. (Cl. 115-16) This invention relates to water craft and more particularly to improvements in hydrojet propulsion systems for watercraft.

It is a principal object of the invention to provide a hydrojet propulsion system of maximum efficiency for watercraft with which maximum propulsive thrust can be obtained on the watercraft with a given prime mover of minimum power.

It is another object of the invention to provide such a propulsion system in which hydrojet propulsive thrust can be developed with a non-positive displacement pump which takes water in from the body of water in which the craft floats and delivers the water as a high velocity jet stream, the reactive thrust of which propels the craft.

It is another object of the invention to provide such a propulsion system in which large volumes of water may be handled and accelerated by the pump at high velocities without inducing cavitation in the pump.

It is another object of the invention to provide such a propulsion system with which maximum speed may be obtained with a given hull and a prime mover of given power.

It is another object of the invention to provide such a propulsion system with which pump cavitation can be mixed axial and radial flow type though other pumps having other types of impellers or propellers may be emeliminated and maximum thrust can be obtained at varying speeds of the craft in water.

It is another object of the invention to provide such a propulsion system which can be constructed as simply and inexpensively as possible.

Other objects and advantages of the invention will become apparent from the following description read in conjunction with the attached drawings in which:

FIG. 1 is a view in side elevation, partially broken away, of a water craft constructed in accordance with this invention;

FIG. 2 is a vertical sectional View of a portion of the propulsion system shown in FIG. 1, and

FIG. 3 is a schematic diagram of the water intake passageway of the propulsion system illustrating the geometry thereof.

The watercraft illustrated in FIG. 1 comprises a hull 10 having a bottom hull portion 12 with a prime mover 14, here illustrated as an internal combustion engine, mounted in the hull and connected to a non-positive displacement pump 16 by a drive shaft 18. A pump intake manifold 20 connects the pump to a port 22 (see FIG. 2) in the bottom portion 12 of the hull, and the pump has a fluid discharge port 24 (see FIG. 2) through which water flowing through the pump emanates as a high velocity jet stream for propelling the craft. A steering and reversing mechanism 26 is mounted on the hull 10 for manipulating the jet stream which emanates from the pump. A preferred steering and reversing mechanism 26 is shown in my co-pending patent application, Serial No. 112,273 filed May 24, 1961, now Patent Number 3,052,- 093, granted September 4, 1962.

Referring now in greater detail to FIG. 2, the nonpositive displacement pump 16 illustrated therein has an impeller 28 rotatably mounted in a fixed flow director 30 and supported by a thrust bearing 32 in a boss 34 on the intake manifold 20. Suitable packing rings 36 are provided in the thrust bearing 32 to maintain a fluid seal around the drive shaft 18 on which the impeller 28 is mounted. It will be noted that the impeller 28 is of the ployed. The impeller 28 has a fluid receiving portion or eye 38 which is referred to herein as the intake port of the pump; it should be noted that the aperture in the pump housing 16 at the left hand end thereof is larger than the eye of the impeller, but the term intake port denotes only that portion of the opening in the pump housing through which fluid is drawn by the impeller during operation of the pump.

The intake manifold 20 has an elongated curved intake passageway therethrough communicating at its lower end with the port 22 in the hull bottom 12 and communicating at its upper end with the intake port 38 of the pump. The cross sectional area of the intake passageway is generally circular at each cross section and this cross sectional area at the upper end is equal to the area of the intake port 38.

As illustrated schematically in FIG. 3, the intake passageway has a central axis 40 extending along the locus of midpoints of the cross sectional areas of the passageway. The axis 40 at the upper end 42 of the intake passageway is colinear with the axis of rotation of the impeller 28, and the cross sectional area of the intake passageway is substantially constant along its length with the sidewalls of the passageway diverging as the walls extend from the upper end 42 to the port 22 in the hull bottom. As indicated in FIG. 3 the side walls diverge from the axis 40 of the passageway by an angle A which should be between one-half and seven degrees and preferably between one and two degrees. This divergence of the side walls of the intake passageway, or viewed in reverse this convergence of the side walls as water flows into the passageway, eliminates turbulence of the water flowing in the intake passageway and provides for delivery of water to the intake port 38 of the pump with substantially laminar flow.

At the lower end of the intake passageway, the axis 40 of the passageway is inclined to the bottom wall 12 of the hull by an angle B which is selected as explained hereinafter to provide that water entering the intake passageway at a designed velocity of the hull in water and a designed speed of the pump will have a horizontal component equal to the velocity of water flow past the hull; in this designed condition of the hull .and pump, the work done by the pump in moving water through the intake passageway is done only in lifting the water from the hull bottom 12 to the impeller, and turbulence in the intake passageway caused by water entering from the stream of water flowing past the hull is eliminated. While the angle B may be selected for a design speed of the hull below its designed maximum speed, it is preferable to select the angle B for the designed maximum speed at which the hull will be moved through water by the prime mover 14 and pump 16 which are to be used with the particular hull; this selection of the angle B for the maximum design speed of the hull insures that maximum speed may be obtained without excessive sacrifice in operating efliciency at speeds below the maximum speed since the turbulence introduced into the intake passageway from the stream of water flowing past the hull bottom becomes a more serious problem as the speed of that stream of water increases.

The selection of the proper angle B is accomplished when the prime mover 14 and pump 16 are selected for a particular hull where the velocity of the jet stream emanating from the discharge end 24 of the pump at maximum hull speed is known; this velocity will normally be on the order of about three times the hull velocity through the water. With the discharge velocity of the pump known, the intake velocity through the port 38 is known since the area of the intake port 38 is to the discharge velocity as the intake velocity is to the area of the discharge port 24. Since the cross sectional area of the iii-- take passageway in the manifold is substantially constant throughout its length, the intake velocity of water along the axis 40 at the port .22 in the hull bottom is substan. tially equal to the intake velocity at the port 38 of the pump.- This intake velocity along the axis 40 is indicated by the vector 44 in FIG. 3, and the design velocity of the hull is indicated by the vector 46. With the design velocity represented by vectors 44 and 46 being knovm, the angle B is selected as the angle whose cosine equalsthe velocity 46 divided by the velocity 44 so that the velocity 46 will be the component of the velocity 44 parallel to the hull bottom 12.

When the proper angle B is selected for the design conditions of the hull and propulsive system, and when the proper divergence of the intake passageway walls is employed, substantially laminar flow in the intake passageway is obtained at the intake port 38 of the pump, and the system operates with maximum efiiciency while cavitation in the pump is prevented throughout substantially the complete operating range of the system.

While one specific embodiment of the invention has been illustrated and described herein, it is obvious that many modifications thereof may be made without departing from the spirit and scope of the invention.

I claim:

1. In a watercraft having a hull adapted to float in a body of water, a non-positive displacement pump mounted on said hull and having intake and discharge ports with said discharge port positioned to deliver a generally horizontal jet of water for propelling said craft, a prime mover connected to said pump for driving said pump, and means defining an intake passageway communicating through said hull for conveying water from the body of water in which said hull floats to said intake port, the improved propulsion system in which:

(a) said intake passageway has a first end communicating with said body of water, a second end communicating with said intake port and a central axis extending between said first and second ends along the locus of 'midpoints of the cross-sectional areas of said passageway;

(b) the cross-sectional area of said second end is substantially equal to the cross-sectional area of said intake port;

() the walls of said intake passageway extend uniformly from said second end to said first end, diverging from said axis by an angle of between /2 and 7 degrees throughout substantially the full length of said passageway;

(d) said pump has a drive member rotatably mounted therein and connected to said prime mover to be rotated thereby with said drive member having an area of revolution through which water is received to be driven by said drive member, and said area of revolution defines said intake port;

(c) said axis of said intake passageway at said second end thereof is colinear with the axis of rotation of said drive member;

(1) said hull has a bottom portion through which said first end of said passageway extends and which defines a path for water flow past said hull as said hull is propelled through the water;

(g) said hull and propulsion system have a design hull velocity through the water at which said pump operates at a design speed and receives water through said intake port at a design intake velocity which exceeds said hull velocity; and,

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(It) said axis of said intake passageway at said first end thereof is inclined to said path for water fiow at approximately the angle whose cosine equals said hull velocity divided by said intake velocity whereby the velocity of water entering said intake passageway at said first end has a velocity component parallel to said path for water flow which is equal to said design hull velocity.

2. The improved watercraft propulsion system of claim 1 in which said design h-ull velocity is approximately the maximum velocity at which said hull will be moved through the water by said propulsion system and said design intake velocity is approximately the intake velocity of said pump when said drive member is driven at maximum speed by said prime mover.

3. In a watercraft having a hull adapted to float in a body of water, a hull surface portion defining a flow path for water flow past said hull responsive to propulsion of said hull through the water, a non-positive displacement pump mounted on said hull and having intake and discharge ports with said discharge port positioned to deliver a generally horizontal jet of water for propelling said craft, a prime mover connected to said pump for driving said pump, and means defining an intake passageway communicating through said hull adjacent to said hull surface portion for conveying water from the body of water in which said hull floats to said intake port, the improved propulsion system in which: said intake passageway has a first end communicating with said body of Water, a second end communicating with said intake port and a central axis extending between said first and second ends along the locus of midpoints of the cross sectional areas of said passageway; said hull and propulsion system have a design hull velocity through the water at which said pump operates at a design speed and pumps water through said first end of said intake passageway at a design intake velocity which exceeds said design hull velocity, and said axis of said intake passageway at said first end thereof is inclined to said flow stream at approximately the angle whose cosine equals said design hull velocity divided by said design intake velocity whereby the velocity of water entering said intake passageway at said first end thereof has a velocity component parallel to said flow stream which is equal to said design hull velocity.

4. The improved watercraft propulsion system of claim 3 in which said design hull velocity is approximately the maximum velocity at which said hull will be moved through water by said propulsion system, and said design intake velocity is the velocity at which water will be moved through said intake passageway by said pump when said pump is driven at maximum speed by said prime mover.

References Cited in the file of this patent UNITED STATES PATENTS 1,055,588 Wood Mar. 11, 1913 1,345,655 Wood July 6, 1920 3,030,909 Barnes Apr. 24, 1962 3,040,527 Christensen June 26, 1962 3,044,260 Hamilton July 17, 1962 FOREIGN PATENTS 1,083,468 France Jan. 10, 1955 278,838 Great Britain Oct. 20, 1927 304,476 Italy Jan. 9, 1933 308,424 Italy July 5, 1933 

3. IN A WATERCRAFT HAVING A HULL ADAPTED TO FLOAT IN A BODY OF WATER, A HULL SURFACE PORTION DEFINING A FLOW PATH FOR WATER FLOW PAST SAID HULL RESPONSIVE TO PROPULSION OF SAID HULL THROUGH THE WATER, A NON-POSITIVE DISPLACEMENT PUMP MOUNTED ON SAID HULL AND HAVING INTAKE AND DISCHARGE PORTS WITH SAID DISCHARGE PORT POSITIONED TO DELIVER A GENERALLY HORIZONTAL JET OF WATER FOR PROPELLING SAID CRAFT, A PRIME MOVER CONNECTED TO SAID PUMP FOR DRIVING SAID PUMP, AND MEANS DEFINING AN INTAKE PASSAGEWAY COMMUNICATING THROUGH SAID HULL ADJACENT TO SAID HULL SURFACE PORTION FOR CONVEYING WATER FROM THE BODY OF WATER IN WHICH SAID HULL FLOATS TO SAID INTAKE PORT, THE IMPROVED PROPULSION SYSTEM IN WHICH: SAID INTAKE PASSAGEWAY HAS A FIRST END COMMUNICATING WITH SAID INTAKE OF WATER, A SECOND END COMMUNICATING WITH SAID INTAKE PORT AND A CENTRAL AXIS EXTENDING BETWEEN SAID FIRST AND 